tells TVGuide.com. "It's kind of shot like 24 and everyone's life is in danger. It's lockdown at the Jeffersonian."When a journalist dies at a biohazard facility, the Jeffersonian team must find the cause of death of prevent a viral outbreak. But when squintern Arastoo (Pej Vahdat) accidentally pricks himself on one of the bones, the race to find the killer — and a cure — heats up."[The disease] is progressive," Vahdat says. "It's extremely fast-moving. Mayhem ensues. ... It gets personal for the team." And it's incredibly personal for Arastoo. "He's an outsider," Vahdat says. "He's just a squintern who covered up his accent. He has insecurity of, 'Are they really allowing me in?' [He] realizes that, whatever competitiveness may take place day to day, ultimately it's a family. And when a family member is in trouble, you drop everything to help them as much as you can."

Of course, some team members are more affected that others. In particular, the ordeal will be difficult for Cam (Tamara Taylor), who hid her romantic relationship with Arastoo for much of the season before recently going public. "[This] crisis deepens their relationship quite a bit," Nathan teases. Adds Vahdat: "It definitely clarifies for Arastoo how much he loves her... and his love for her grows. When you're facing something terminal, all your senses are heightened. And... for certain people, you don't want to lose them. And he sees the woman he's in love with also show that she cares for him."But are Arastoo and the relationship doomed? After all, just two seasons ago, producers killed off a squintern in the penultimate episode. "Well if it's happened once before, it's certainly possible it could happen again," Vahdat says with a laugh. Either way, the threat of mortality will have an impact on everyone, especially Dr. Brennan (Emily Deschanel), who is separated from Booth (David Boreanaz) throughout the episode because of the lockdown. And those feelings will definitely spill over into the finale.

"It freaks her out in her own way," Deschanel says. "The outbreak puts a seed in Brennan's mind about how delicate our lives are. Now she as a daughter and Booth and she can't help but internalize how devastating it would be to lose Booth. That kind of sets us up for the last episode and plays a big part in the season finale."Bones airs Mondays at 8/7c on Fox.